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            <h2 class="title" style="clear: both"><a id="transapp_why"></a>Why transactions?</h2>
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      <p>
        Perhaps the first question to answer is "Why transactions?"
        There are a number of reasons to include transactional support
        in your applications. The most common ones are the
        following:
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            <span class="term">Recoverability</span>
          </dt>
          <dd>
                Applications often need to ensure that no matter
                how the system or application fails, previously saved
                data is available the next time the application runs.
                This is often called Durability.
            </dd>
          <dt>
            <span class="term">Atomicity</span>
          </dt>
          <dd>
                Applications may need to make multiple changes
                to one or more databases, but ensure that either all
                of the changes happen, or none of them happens.
                Transactions guarantee that a group of changes are
                atomic; that is, if the application or system fails,
                either all of the changes to the databases will appear
                when the application next runs, or none of
                them.
            </dd>
          <dt>
            <span class="term">Isolation</span>
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          <dd>
                Applications may need to make changes in
                isolation, that is, ensure that only a single thread
                of control is modifying a key/data pair at a time.
                Transactions ensure each thread of control sees all
                records as if all other transactions either completed
                before or after its transaction.
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